Spring group

ABSTRACT

A snubbed spring group comprising a tandem arrangement of first and second deflectable load bearing structures that interact in series for transmitting load forces therethrough. One of the structures is a solid body of elastomeric material, preferably polyurethane, having a hardness in the range from about 60 to about 90 Shore A. The other preferably is a coil spring having a spring rate that is a small fraction of that of the body of elastomeric material.

Unite States Patent MacDonnell 1 1 Oct. 2, 1973 1 1 SPRING GROUP1,936,389 11 1933 Hallquist 267/4 x 2,322,879 6/1943 Piron 267/3 X [75]Inventor: Robert W. MacDonnell, rcte, 111. 3321764 6/1967 Johnson H248/358 AA X [73] Assignee: Unity Railway Supply Co. Inc.,

Chicago, Ill Primary Examiner-Gerald M. Forlenza AssistantExaminer-Howard Beltran 2 97 I2 1 Flled Apr 1 0 Attorney-E. MannlngG1les and 11. Patnck Cagney [2]] App]. No.: 25,973

[57] ABSTRACT [52] US. Cl ..267/3, 105/197 A, 105/197 D, H

OS/I97 R 248/358 R, 267/33 A snubbed sprmg group compnsmg a tandemarrange- [51] Int Cl B6 5/06 5/08 B6 5/12 ment of first and seconddeflec table load bearing struc- Field 05/19; A 197 R tures thatinteract in series for. transmitting load forces 105/197 63 5therethrough. One of the structures is a solid body of 358 R elastomericmaterial, preferalily polyurethane, having a hardness in the range fromabout 60 to about 90 [56] References Cited Shore A. The other preferablyis a coil spring having a UNITED STATES PATENTS spring rate that is asmall fraction of that of the body of elastomeric material. 137,2954/1373 Daniels 267/3 139,862 6/1873 Bridges 5 Claims, 12 Drawing,Figures PATENTED 2 75 SHEET 3 IF 4 |||1|||||||l lllllllllllllllill [V4ll/2 COMPRESSIVE DEFLECTION (INCHES)- muons/foe Z WZ'ZZ WZCZMeKZarraemmx PAIENTEBUU 3.762.694

SHEET U- UF 4 f 40 6 4@ 42 U a4 44 Q Q Q W. wa

COMPRESSION-DEFLECTION CHARACTERISTICS T 0F SOFT URETHANES ,SHAPE FACTOR0 lo 0 lo 20 30 40 5o COMPRESSIVE STRAIN, e

SPRING GROUP BACKGROUND OF THE INVENTION This invention relates toenergy dissipating cushioning mechanisms and more particularly isconcerned with a snubber for stabilized freight car trucks.

The railroad field has many applications requiring cushion arrangementsthat can provide both high load bearing ability and high energydissipating characteristics. The environment imposes fixed constraintssuch as short cushion travel (typically 2 to 5 inches) and smallmounting pockets for most railway cushioning devices includingparticularly snubbers of the type that are incorporated in the springgroups that support the trunk bolster from the side trains in the caseof stabilized freight car trunks. There is a growing need for a snubberof more effective load bearing and energy dissipating characteristicsoccasioned by the trend in the railroad industry to employ faster andlonger freight trains with more heavily loaded cars. Because the carload capacity and travel speeds have increased aggressively over theyears, the cyclic bolster ride forces can exceed the load capacity ofthe spring groups with or without the use of conventional snubberswithin such spring groups. When the ride forces exceed the supportcapacity of the spring groups, the coil springs go solid, thus causinghigh shock loading at the bolster and spring group mounting locations.Such shock loading reduces spring life requiring frequent replacementand greatly increases the danger of service failure of the bolster.

SUMMARY OF THE INVENTION The present invention provides a snubbercapable of dissipating a substantial portion of the ride energy whilesatisfying the environmental constraints of a deflection range limitedto 2 to 4 inches and dynamic bolster load forces in excess of 100,000pounds. In addition, the snubbers exhibiting these high performancecharacteristics are arranged to provide a soft ride under light loadconditions.

In accordance with the present invention, a snubber includes first andsecond deflectable load bearing structures mounted in tandem forinteraction in series for transmitting load forces therethrough. One ofthe structures includes one or more bodies of polyurethane materialhaving hardnesses within the range from about 60 to about 90 Shore A.The other structure preferably is a coil spring but can be anyresiliently deflectable structure characterized in having a spring ratethat is a small fraction of the spring rate of polyurethane body orbodies. The coil spring provides for a soft ride under light loadcondition. Under heavier load conditions the coil spring deflects fullstroke and the polyurethane body or bodies alone provides cushioning.

Other features and advantages of the invention will be apparent from thefollowing description and claims and are illustrated in the accompanyingdrawings which show structure embodying preferred features of thepresent invention and the principles thereof, and what is now consideredto be the best mode in which to apply these principles.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings forming apart of the specification, and in which like numerals are employed todesignate like parts throughout the same:

FIG. 1 is a fragmentary side elevational view of a stat bilized freightcar truck of ton capacity;

FIG. 2 is a fragmentary sectional view taken as indicated on the line2-2 of FIG. 1;

FIG. 3 is a fragmentary plan sectional view taken as indicated on theline 3-3 of FIG. 2 to better disclose the mounting locations of thesnubber units;

FIG. 4 is an enlarged vertical sectional view illustrating oneembodiment of a snubber constructed in accordance with the presentinvention;

FIG. 5 is similar to FIG. 4 and shows the snubber under static fullyloaded conditions;

FIG. 6 is a graph depicting the load-deflection characteristics of thesnubber of FIGS. 4 and 5;

FIGS. 7-11 are each vertical transverse sectional view showingadditional snubber embodiments; and

FIG. 12 is a series of graphs showing compressiondeflectioncharacteristics of urethane of various hardnesses and shapes.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, andspecifially to FIGS. l-3, the invention as disclosed herein is embodiedas a snubber that is shown incorporated in a bolster spring group of astabilized freight car truck to increase the load bearing capacitythereof and to increase the energy dissipation characteristics thereof.

The truck is of any conventional type and for purposes of disclosure a100 ton, Type S-2-C, stabilized freight car truck is shown as includinga side frame 1 1 having a top compression section llT, a bottom tensionsection 11B and spaced side columns 118 defining a bolster windowopening 12. A bolster 13 is bridged between a pair of side frames 11 andhas its opposite ends projecting into the bolster openings to ride on aspring group, generally designated at 14, disposed within each bolsterwindow opening. The bottom tension section 11B of the side frame servesas a lower spring seat and includes a number of flange portions 11F forlocating and retaining the lower ends of the springs that make up thebolster spring group 14. The underface of the bolster 13 serves as anupper spring seat.

In the illustrated arrangement, each end of the bolster is provided witha pair of friction housings 13H arranged in back-to-back relationshipand each mounting a friction block 138 to be loaded against a wear plate11W on the corresponding side column 118 to provide africtionaldissipation of energy during bolster movement. Integral guideflanges 13F on the bolster flank the side columns 115.

The bolster spring groups for the 100 ton car have nine spring positionsin a 3 X 3 array as best shown in FIG. 3. The center row end positionsare occupied by stabilizing springs 15 that act to load the frictionblocks 138 against the wear plates 11W on the side columns in a wellknown fashion. The seven remaining spring positions are normallyoccupied by D-S springs which offer a maximum travel of 3-11/16 inchesbut snubbers are frequently used to replace one or more of the D Ssprings. Currently, such snubbers have a load capacity of up to about15,000 pounds per unit and about a 50 percent dissipation, whereas theloading of the cars frequently imposes substantially greater loads thancan be handled by conventional snubbers.

For example, taking the case of the typical 100 ton car, the car weightempty is about 68,000 pounds and with full revenue load is about 150,000pounds. These values are distributed over four spring groups so thateach group must handle an empty load of 17,000 pounds and a revenue loadof 54,500 pounds. These values are for static conditions and areincreased several fold under the dynamic conditions of high speedservice. Each spring position of each spring group, assuming use of D-Souter and inner coil springs offers a solid capacity of about 12,000pounds. Therefore, in the illustrated arrangement, the seven springpositions provide a solid capacity of 84,000 pounds. If conventionalsnubbers (15,000 pound capacity) are used at two of these seven springpositions, the solid capacity of the group is increased to 90,000pounds.

Under high speed conditions, the stabilizing friction blocks and theconventional snubbers exert an energy dissipating function forcontrolling the bolster ride but the bouncing or rocking energy impartedto the bolster exceeds the energy dissipation and leads to excessivecompression and recoil action tending to drive the bolster springs solidand to overstress the snubbers.

In accordance with the present invention, an improved snubber unit 16 isprovided offering greatly increased load capacity and energydissipation. In the illustrated arrangement, a pair of these snubberunits 16 occupy the endmost positions in the outer row of springs.Alternatively, a pair of snubbers can be located in diametricallyopposite corners of each spring array of a single snubber can be locatedin any one of the central positions. In general, any symmetricalmounting arrangement can be employed and is contemplated in the practiceof the present invention.

Briefly, a snubber of the present invention will be seen to comprise atandem arrangement of cushioning structures interacting in series. Amain cushion ele ment, generally indicated by the letter U, comprisessolid elastomeric material capable of exhibiting high strength andenergy dissipation characteristics such as polyurethane. A secondelement is illustrated as a coil spring S having a spring constant thatis a small fraction of the spring constant of the elastomeric or maincushion U so that the coil spring cushion S reaches substantially fullstroke deflection before any substantial compression of the maincushion. A floatingspring seat connects the main cushion in tandemrelation with the coil spring cushion.

Turning to FIGS. 4 and 5, a preferred snubber embodiment is disclosedherein for application in 100 ton freight cars in which the conventionalsprings of the spring group 14 are of the D-5 type, having a free heightof inches. Therefore, the snubber unit has a normal free height'of 10-%inches plus approximately 'rfi inch to allow for initial permanentsetting of the unrethane comprising the main cushion structure.

The snubber embodiment shown in FIG. 4 employs a spring seat 19 in theform of an inverted hat-shaped metal casting which defines a well openat the top and bounded by an annular rim or shoulder 19A. The well,which is of natural draft, is 3 inches deep, 2-% inches in diameter atthe base, and 3 inches in diameter at the top. A coil spring S encirclesthe well and supports the underface of the spring seat at a distance of1-% inch above the floor as defined by the side frame. The main cushionU comprises a center cylinder 17 of 60 to 70 Shore A durometer hardnessurethane, and an auxiliary sleeve 17B of 80 to 90 Shore A durometerurethane. The center cylinder 17 is 8 inches in height and 2J6 inches indiameter, it being formed in place so that its load face is securelyadhered to the inner face of base wall 198 of the well. The auxiliarysleeve 17B is shown mounted upon the rim 19A to extend alongside andencircle an intermediate length region of the center cylinder 17. Thesleeve 178 has a free height of 3-% inches, an outer diameter of 5%inches, and an inner diameter of 3% inches, to provide a nominalclearance gap under free load of inches for radial expansion of thecenter cylinder cushion 17. The contact face of the aleeve 17B issecurely adhered to the shoulder 19A to maintain a constant load areaand the upper extremity of the sleeve 17B terminates 1% inches below theupper extremity of the center cylinder 17 in free height relationships.As stated, the clearance between the underface of the well and the flooris 1% inches so that the initial deflection of the coil spring providessoft cushioning action under light load conditions. Full strokedeflection of spring S is slightly less than 1% inches so that theunderface of the spring seat 19 restricts deflection of the spring priorto full stroke deflection thereof preventing damage to the spring S whenthe load forces exceed its load capacity. After the underface of springseat 19 abuts against the floor, the center cylinder 17 begins todeflect.

The normal condition of the snubber under static full load conditions ina ton car is represented in FIG. 5 wherein the unit is shown to havebeen deflected a total amount of approximately 3 inches. Since the coilspring S provided substantially the first 1% inches of deflection, theelastomeric main cushion U has been deflected 1% inches. At this loadcondition, no clearance exists between the center cylinder cushion l7and the wall of the well and between the center cylinder cushion 17 andthe surrounding sleeve 17 B. It will be noted that when the loading issuch to drive the elastomeric cushion U snubber into a fully compressedsolid condition, the arrangement automatically undergoes an abruptchange in cushioning characteristics. Prior to full closure, the centercushion l7 expands into contact with the wall of the well and intocontact with the surrounding sleeve 17B. The portion of the centercylinder cushion 17 which is within the well is inactive upon furtherdeflection so that the final deflection is determined by the combinedeffect of the sleeve 17B and the portion of the center cylinder cushion17 which is above the shoulder 19A.

FIG. 6 is a graph of the load-deflection curve of the snubber of FIGS. 4and 5. In FIG. 6 the curve 20 represents the compressive strain of theelastomeric main cushion U in response to loads up to approximately15,500 pounds. Portion A of curve 20 is representative of the cushioningeffects of the snubber when onl the central cylinder cushion 17 is underload and subject to deflection. The remaining portion of curve 20represents the cushioning characteristics of the snubber after thecenter cylinder cushion l7 expands into contact with the wall of thewell and into contact with the surrounding sleeve 17B. Curve 21represents the return characteristics of the main cushion U of thesnubber. The area enclosed by the two curves 20, 21, therefore, definesthe amount energy dissipation of the snubber per cycle.

It will be noted that the maximum available deflection stroke for thesnubber is determined by the D-5 springs which go solid after 3-1 1/16inch deflection. In the illustrated arrangement, this deflection strokeineludes l inch of travel of the coil spring S which is substantiallyfully compressed before any significant compression of the urethane maincushioning element and a final 2-3/l6 inch of travel which isaccommodated by the urethane main cushioning body. It is important tonote, however, that complete deflection of the D-5 springs and maximumavailable deflection of the snubber is prevented both because of theamount of energy dissipation provided by the snubber during a deflectioncycle and because of the great load carrying capacity of the maincushioning body U. For example, the snubber of FIGS. 4 and 5 is capableof carrying a load of 21,550 lbs. at full available deflection of 2-3/16inches.

A snubber constructed in accordance with FIGS. 4 and 5 is capable ofhandling a cycle rate of deflection and release of 40 per minute undertypical full load conditions.

Certain generalities apply to the snubber arrangement of the presentinvention. The shape and hardness of the main cushioning element Udetermines to a large extent the snubbers load bearing and cushioningcharacteristics. The effect of shape and hardness can be seen withreference to FIG. 12, which depicts compression-deflectioncharacteristics of urethanes of various hardness and shapes. The shapefactor is computed according to the following formula:

Shape Factor Area of Load/Area of Free Side Faces Thus, in the case ofcylinders the shape factor formula is given as:

Shape Factor D/4H where D is the cylinder diameter and H is the cylinderheight.

The general shape factor formula is generally applicable where theelastomeric structures have load faces which are parallel and restrainedfrom lateral movement and where the structure thickness is not more thantwice the smallest lateral dimension. From FIG. 12 it can be seen thatthe configuration of the main cushioning element U can be easilytailored to meet requirements posed by specific freight carapplications.

There is one restriction to the configuration and that is that thedeflection ratio that the main cushioning'element U be subject be lessthan about percent of its height in order to preserve the useful life ofthe urethane under the cyclic load conditions they usually obtain.

Turning now toFIGS. 7 to ill, a number of alternate snubber embodimentsare shown, each of which will be described for use in a 100 ton freightcar truck having D-5 main springs.

The snubber of FIG. 7 comprises a cylindrically shaped urethane body 22which typically is 5 inches in diameter and 5% inches in height. Thespring seat 24 is 54 inch thick and the coil spring S has a free heightof 4% inches and a 5% inch OD. The urethane body 22 typically has aShore A durometer hardness of 70 to 90. The spring seat 24 includes adepending annular wall portion 24A which under no load is spaced 2-l1/16 inches above the floor upon whicn the coil spring seats so that themaximum deflection of the coil'spring is slightly less than 2-1 l/l6inches.

Another snubber embodiment is shown in FIG. 8 wherein the same basicarrangement as that of FIG. 7 is employed with there being an auxiliarycushion 26 of urethane located within the well defined by the dependingannular wall 24A. The auxiliary cushion 26 has a nominal clearance of2-3/16 inches so that it comes under load during the last half inch ofdeflection of the coil spring. It preferably has a lower hardness thanthe urethane in the upper cushion though it may be of identical hardnessif desired. In this form, the spring seat is shown with a centralthrough hole 28 so that the upper and lower urethane cushions 22, 26 maybe poured at the same time even where different durometer materials areused for each. The cushions being poured in place have the load facesthereof securely bonded to the spring seat 24 to maintain fixed diameterrelationships under all load conditions.

A further snubber embodiment is shown in FIG. 9 which is basedessentially upon the embodiment shown in FIG. 8 except that the mainupper cushion U is divided into a central cushion 30 of slightly greaterheight and a surrounding sleeve 32. In this form, the auxiliary cushion34 is poured simultaneously with the central cushion 30 in the fashionpreviously described and the auxiliary cushion 34 comes under loadbefore the coil springs reaches final deflection so that the centralcushion 30 also begins to come under load in proportion to the action ofthe auxiliary cushion 34. After the central cushion 30 is deflected tothe plane of the sleeve 32, an annular clearance will remain until thesleeve 32 and central cushion 30 have both been further deflected.Before final solid closure condition is reached, the central cushion 30and sleeve 32 will come into contact and automatically generate a newshape factor condition to offer substantial increased resistance duringfinal deflection.

Another snubber embodiment is shown in FIG. 10 which is similar to thearrangement of FIGS. 4 and 5 in the use of an inverted hat-shaped springseat 36 and an 8 inches high central urethane cushion 38 seated in andprojecting above this spring seat. In this arrangement, a pair ofsurrounding sleeves 40, 42 are employed. The inner sleeve 40 is again of3% inches free height and has a inches clearance space relative to thecentral cushion 38. The outer sleeve 42 is about 3% inches in freeheight and is of substantially higher durometer than the center cushion38 or the first sleeve 40 to effectively serve as a high resistanceurethane stop for the final stages of deflection.

Still a further snubber embodiment is shown in FIG. 11 wherein thespring seat 44 is shown supporting a set of three urethane cushionsincluding an outer sleeve 46 having a free height of 5 inches, an innersleeve 48 having a free height of 4 inches, and a central core 50 havinga free height of 3% inches. The outer sleeve 46 is of 60 durometer, theinner sleeve 48 of durometer, and the central core 50 of durometerurethane; the annular gap between the sleeves 46, 48 is A inches and theannular gap between the innter sleeve 48 and the central core 50 is Ainches. When upon loading of the unit, the coil spring will take thefirst 1 /2 inches deflection and the outer sleeve 46 will then take 1inches of deflection with there remaining a clearance gap at this pointrelative to the inner sleeve 48. Subsequent deflection of the twosleeves 46, 48 simultaneously is governed by their individual shapefactors until the end space of the central cushion 50 is reached and atapproximately that point all of the cushions interengage laterally anddefine a common shape factor of substantially increased resistancecharacteristics.

Thus, while preferred constructional features of the invention areembodied in the structure illustrated herein, it is to be understoodthat changes and variations may be made by those skilled in the artwithout departing from the spirit and scope of the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. In an energy dissipating cushioning mechanism that includes a tandemarrangement having first and second deflectable load bearing structuresinteracting in series for transmitting load forces therethrough, theimprovement wherein one of said structures includes concentric inner andouter bodies each being of compressible urethane material having ahardness in the range from about 60 to about 90 Shore A, means mountingsaid inner and outer bodies in radially spaced relation to undergodeflection along a common axis, with said bodies, when free of load,presenting load receiving surfaces in an axially offset relation andsaid bodies having load bearing determining shapes wherein one of saidbodies undergoes individual initial axial compression for substantiallycarrying the static load forces and wherein said bodies undergo jointaxial compression in radially contacting relation to dissipate energy inreacting to additional travel due to load oscillation, the other of saidstructures comprises a coil spring having a spring rate that is a smallfraction of the spring rates of either of said bodies whereby said coilspring is deflectable through substantially full stroke prior tosubstantial deflection of either of said bodies and said arrangementincludes means to restrict deflection of said coil spring prior to fullstroke deflection thereof thereby preventing damage to said coil springwhen said load forces exceed the load capacity of said coil spring.

2. In an arrangement as defined in claim 1 and wherein said inner bodyis longer than said outer body.

3. In an arrangement as defined in claim 1 and wherein said outer bodyis longer than said inner body.

4. In an arrangement as defined in claim 1 and wherein the axial travelcorresponding to said joint axial compression is substantially less thanthe axial travel corresponding to said individual axial compression.

5. In an arrangement as defined in claim 1 and wherein said bodies arein radial contact after the limit of said initial individual travel andwherein the axial travel corresponding to said joint axial compressionis substantially less than the axial travel corresponding to saidindividual axial compression.

1. In an energy dissipating cushioning mechanism that includes a tandemarrangement having first and second deflectable load bearing structuresinteracting in series for transmitting load forces therethrough, theimprovement wherein one of said structures includes concentric inner andouter bodies each being of compressible urethane material having ahardness in the range from about 60 to about 90 Shore A, means mountingsaid inner and outer bodies in radially spaced relation to undergodeflection along a common axis, with said bodies, when free of load,presenting load receiving surfaces in an axially offset relation andsaid bodies having load bearing determining shapes wherein one of saidbodies undergoes individual initial axial compression for substantiallycarrying the static load forces and wherein said bodies undergo jointaxial compression in radially contacting relation to dissipate energy inreacting to additional travel due to load oscillation, the other of saidstructures comprises a coil spring having a spring rate that is a smallfraction of the spring rates of either of said bodies whereby said coilspring is deflectable through substantially fulL stroke prior tosubstantial deflection of either of said bodies and said arrangementincludes means to restrict deflection of said coil spring prior to fullstroke deflection thereof thereby preventing damage to said coil springwhen said load forces exceed the load capacity of said coil spring. 2.In an arrangement as defined in claim 1 and wherein said inner body islonger than said outer body.
 3. In an arrangement as defined in claim 1and wherein said outer body is longer than said inner body.
 4. In anarrangement as defined in claim 1 and wherein the axial travelcorresponding to said joint axial compression is substantially less thanthe axial travel corresponding to said individual axial compression. 5.In an arrangement as defined in claim 1 and wherein said bodies are inradial contact after the limit of said initial individual travel andwherein the axial travel corresponding to said joint axial compressionis substantially less than the axial travel corresponding to saidindividual axial compression.